1. Field of the Invention
This invention relates to a method for making a spindle for an axle and, more particularly, to a method of forming a tubular blank having a uniform cross section and thickness to provide the general contour of the spindle and then securing a collar thereon to act as a bearing stop.
2. Description of the Prior Art
There remains a continuing need for reliable, safe and lightweight axles and/or axle spindles for heavy duty trucks and trailers. An axle of this general type is disclosed in U.S. Pat. No. 3,037,818 to include at each spindle an outer first bearing and an inner second bearing for supporting the wheels. One area of concern when providing axles and axle spindles for these heavy duty vehicles is that adequate support and strength will be provided in the area of the wheel bearings. Consequently, for the inner wheel bearing, the spindle has generally been provided an integral, radially extending bearing stop and the spindle is generally thickened in this region to provide the desired strength. The bearing stop establishes the location of the wheel relative to the end of the spindle with a retaining nut being used to secure the wheel on the spindle as the inner bearing is forced against the bearing stop. While U.S. Pat. No. 3,037,818 discloses one method for forming such an axle and spindle, U.S. Pat. Nos. 3,465,418; 3,501,202; 3,535,002 and 3,564,896 present different methods for forming the axle but again include the two bearing mounting areas and a rigid, integrally formed bearing stop for the inner bearing.
While there has heretofore been disclosed a number of methods of forming an axle or an axle spindle from a generally tubular blank which might tend to save weight and material, there remains some question regarding the applicability of these methods for the particular heavy duty use for which the present invention is intended. For example, U.S. Pat. Nos. 1,091,751; 2,133,091 and 2,133,092 all disclose how a tubular blank having a uniform external diameter and a uniform thickness can be generally formed to provide the bearing mounting regions mentioned above for support of a vehicle wheel. However, since no provision is specifically made in these axle spindle configurations for providing a rigid bearing stop for the inner bearing, it is doubtful that such axle spindles could be utilized in the heavy duty environment expected for the present invention.
U.S. Pat. No. 3,701,564 appears to disclose that a spindle of the desired type can generally be formed by cold working a tubular blank to include a radially extending bearing stop while still maintaining a generally uniform wall thickness. However, there is some doubt that such a product could be satisfactorily employed. Generally, it has been found that the forces on an integrally formed bearing stop for the inner bearing are so significant that the resulting concentration of stresses at the transition between the bearing mounting region and the bearing stop have required the thickness of the spindle to be significantly enlarged in this area.
In fact, there have even been some axle spindles which have been formed from tubular blanks which initially were provided a non-uniform thickness to insure that additional metal would be retained in the bearing mounting region after the basic reduction in this area was completed.
It can be seen that a number of prior art axle spindles are inappropriate for use on heavy duty vehicles since no rigid bearing stop is provided. Other configurations appear to be appropriate for such use but require additional material and weight to provide adequate strength for such a bearing stop when it is integrally formed with the rest of the spindle. The use of any other type of a bearing stop on the spindle may have been considered inadequate for heavy duty use if, in fact, it was ever even considered as an alternative in the past. Although U.S. Pat. No. 313,517 appears to generally disclose that a separate collar may be installed as a bearing stop on an axle, this disclosure would not appear to be applicable for the expected heavy duty use. Rather than requiring two bearings of the present configuration, the disclosed tubular axle requires one large tapered bearing for wheel support. Even though the taper would significantly reduce the forces on the collar, it should be noted that this prior art configuration nevertheless includes a thickened basic spindle and is even provided additional material within the spindle for added strength in the collar region.